Field of the Invention
The present invention relates to a top cap assembly for a secondary battery, and more particularly, to a top cap assembly for a secondary battery which provides improved safety.
Description of the Related Art
Since secondary batteries, which are rechargeable, can be miniaturized and be manufactured to have high capacity, the development and use of secondary batteries are growing. Secondary batteries include: an electrode assembly, which includes an anode, a cathode, and a separator; and an exterior part accommodating and sealing the electrode assembly and electrolyte. Secondary batteries may be classified into cylindrical type secondary batteries, prismatic type secondary batteries, and pouch type secondary batteries according to structural features thereof.
Cylindrical type secondary batteries include a cylindrical can, an electrode assembly accommodated in the cylindrical can, and a top cap assembly coupled to an upper part of the cylindrical can. The top cap assembly finishes the upper end of an opening part of the cylindrical can.
FIG. 1 is a view illustrating a top cap assembly in the related art. Referring to FIG. 1, the top cap assembly includes: a current interrupt device (CID) short-circuiting member 40, which interrupts an electric current when a high voltage is generated in a battery; a safety vent 30 connected to an upper part of the CID short-circuiting member 40 and including a plurality of notches, which are broken when a voltage equal to or greater than an allowable voltage of the CID short-circuiting member 40 is generated, to discharge gas from the battery; a top cap 20 disposed on the uppermost end of an upper opening part of a can 10 of the battery that is a cylindrical type secondary battery; and a gasket 50 surrounding and sealing an outer circumferential surface of the CID short-circuiting member 40.
When the cylindrical type secondary battery undergoes external short-circuiting, the gasket 50 surrounding the CID short-circuiting member 40 may be easily molten and deformed at a high temperature. Accordingly, the possibility that the CID short-circuiting member 40 and the safety vent 30 are brought into contact with and stuck to each other increases. In addition, when the CID short-circuiting member 40 and the safety vent 30 are brought into contact with each other, the CID short-circuiting member 40 and the safety vent 30 fail to interrupt an electric current, and thus, the battery may explode.